1. Field of the Invention
The present invention relates to a small-sized motor, and more particularly relates to a small-sized motor wherein an electric element such as a capacitor is attached to a case cover for being used for the driving of electrical equipment or the like.
2. Description of the Related Art
A small-sized motor is widely used in a vehicle electrical apparatus such as a vehicle door lock opening and closing device, an electrically powered mirror mirror-surface driving and containing device, or an air conditioner. In the case of the small-sized motor and the peripheral equipment like this, the reduction of electric noise caused at the time of operation is required, and regulations are laid down all over the world. CISPR25 as an international standard, GMW3100/3097 as a carmaker standard, or the like can be mentioned.
In order to reduce the electric noise, in the case of a small-sized motor, it is necessary to directly attach the electric element such as a capacitor or a choke coil to the motor. Therefore, conventionally, it has been performed that the electric element is arranged and wired on a printed board, and that this printed board is mounted on the motor. However, in the case of a mounting method like this, such a work is necessary, where a special earth lead wire for earthing the electric circuit is connected to the printed board in advance, and furthermore, this printed board is mounted on a metal case of the motor, and after that, the above described earth lead wire is connected, for example, by soldering.
In order to reduce the man-hour of such a troublesome work, a printed board mounting method as shown in FIG. 6 is conventionally well known (refer to Japanese Utility Model Publication No. 63-127254). In FIG. 6, a printed board 25 to which an electric element (omitted in the drawing) is attached is structured such that it is mounted to a metal case 1 where the motor main body (omitted in the drawing) is contained, and after that, furthermore, it is covered by a case cover (omitted in the drawing).
As shown in the drawing, to the metal case 1, a projecting needle part 26 projected from an opening end edge is provided, and in the meantime, corresponding to this projecting needle part 26, to the printed board 25, an engaging part 28 which makes the projecting needle part 26 pass to an earth electrode part 27 is provided. As shown in the drawing by an alternate long and short dash line and an arrow, in order to make the state where the projecting needle part 26 is inserted into the engaging part 28, the printed board 25 is mounted on the metal case 1, and after that, by performing the soldering of the projecting needle part 26 and the earth electrode part 27, the earth electrode part 27 of the printed board 25 and the metal case 1 are electrically connected through the solder.
Thus, it is enough for the purpose only to perform the soldering on the way of the motor assembling step, and therefore, it becomes possible to largely reduce the working man-hour in the earth executing step. However, in the case of such a prior art, the soldering is still needed as another step different from the motor assembling, and therefore, the reduction of the working man-hour is furthermore required. Furthermore, it is required to attach the electric element to the synthetic resin case cover with a good workability to efficiently attach it in a narrow space.
Therefore, it is an object of the present invention to solve such problems, and to perform the assembling with a good workability in such a way where an electric circuit composed of an electric element such as a chip capacitor attached on a printed board is attached to a case cover, and in the meantime, the earth of the electric circuit is easily and surely body-earthed to the metal case, and the number of the motor assembling steps is reduced.
The small-sized motor of the present invention includes: a hollow cylindrical metal case with a bottom where a magnet is attached to an inside periphery; a synthetic resin case cover which is fitted to close an opening part of the above described case; and a rotor where a laminated core, a winding wound around the above described laminated core, and a commutator are attached on a shaft. To this case cover, a printed board where an electric circuit including an electric element is attached is mounted. The printed board has a soldering part which is connected to a member attached to the interior of the case cover for being connected to an electric power source supplied from the outside and a soldering part which is connected to a projection in a notch provided on the opening part side of the above described metal case for body-earthing the earth of the electric circuit. In the soldering part for the body-earthing, at the time of assembling the motor, a pair of electrodes are brought into contact from the outside of the metal case near the above described soldering part to weld the above described soldering part by the principle of electric resistance welding, after fitting the case cover to the metal case opening part.
In the case of the manufacturing method of a small-sized motor of the present invention, after inserting a rotor where a laminated core, a winding wound around the above described laminated core, and a commutator are attached on a shaft, into a hollow cylindrical metal case with a bottom where a magnet is attached to an inside periphery, a synthetic resin case cover is fitted to close an opening part of the above described case. To the case cover, a printed board where an electric circuit including an electric element is attached is mounted. The printed board has a soldering part which is connected to a member attached to the interior of the case cover for being connected to an electric power source supplied from the outside and a soldering part which is connected to a projection in a notch provided on the opening part side of the above described metal case for body-earthing the earth of the electric circuit. At the time of assembling the motor, after fitting the above described case cover to the metal case opening part, a pair of electrodes are brought into contact from the outside of the metal case near the soldering part for the body-earthing so that the above described soldering part may be welded by the principle of electric resistance welding.